不同精粗比条件下添加支链氨基酸对绵羊瘤胃微生物体外发酵的影响

本试验旨在利用体外发酵培养技术和正交试验设计研究在不同精粗比（20：80、40：60和60：40）条件下添加支链氨基酸（缬氨酸、亮氨酸和异亮氨酸）不同组合对瘤胃微生物体外发酵的影响，并对支链氨基酸间的组合效应进行分析以筛选在不同精粗比底物条件下支链氨基酸的最佳组合。结果表明，无论发酵底物精粗比如何，添加支链氨基酸对体外发酵pH、NDF降解率（NDFD）和乙酸/丙酸均无显著影响（P>0.05），而DM降解率（DMD）在各组合间存在差异。当发酵底物精粗比为20：80时，3种氨基酸对氨态氮（NH₃-N）、挥发性脂肪酸（VFA）、总挥发性脂肪酸（TVFA）的影响均具有组合效应（P<0.05）；其中异丁酸和戊酸水平随缬氨酸添加水平的增加而升高（P<0.01）；异戊酸水平则受亮氨酸和异亮氨酸添加水平的影响（P<0.05）。当发酵底物精粗比为40：60时，异丁酸水平随着缬氨酸添加水平增加而升高（P<0.01）；异戊酸浓度受3种支链氨基酸的影响（P<0.05）。当精粗比为60：40时，添加支链氨基酸主要影响异丁酸、异戊酸和戊酸的水平；其中异丁酸主要受缬氨酸的影响（P<0.01），异戊酸受亮氨酸和异亮氨酸的影响（P<0.01），戊酸受缬氨酸和异亮氨酸的影响（P<0.05）。从异丁酸、戊酸和异戊酸来看，添加3种氨基酸均表现出明显的组合效应（P<0.05）。综上所述，以DMD为指标，当发酵底物精粗比为20：80时，缬氨酸、亮氨酸、异亮氨酸的最佳添加水平为0.67、2.00、1.33 mmol/L；当底物精粗比为40：60和60：40时，无需额外添加3种支链氨基酸。

Effects of Branched Chain Amino Acids on Sheep Rumen Microbial Fermentation in vitro Based on Different Concentrate to Forage Ratios

Methods of in vitro culture technique and orthogonal experimental design were using in this experiment to identify the effects of branched chain amino acids (BCAAs,valine,leucine and isoleucine) on rumen microbial fermentation in vitro based on different concentrate to forage ratio (CFR) of 20:80,40:60 and 60:40,and the best combination of BCAAs on each CFR was gained after analysis of the combination effects of BCAAs.The results showed that the final pH,NDF degradability (NDFD) and acetate/propionate were not affected by BCAAs addition (P>0.05).However,DM degradability (DMD) was significantly different in various combinations.When the CFR was 20:80,the three amino acids showed a combination significant effect on the NH₃-N,VFA and TVFA (P<0.05).Along with the increase of valine levels,the concentrations of isobutyric acid and valeric acid were significantly increased (P<0.01),isovaleric acid was affected by isoleucine and leucine (P<0.05).When the CFR was 40:60,the concentration of isobutyric acid increased with the increase of valine supplementation level (P<0.01).Isovaleric acid was affected by three kinds of BCAAs (P<0.05).When the CFR was 60:40,BCAAs mainly affected the concentrations of isobutyric acid, valeric acid and isovaleric acid.Isobutyric acid was mainly affected by valine (P<0.01),isovaleric acid was affected by leucine and isoleucine (P<0.01),and valeric acid was affected by valine and isoleucine (P<0.05).Based on the concentrations of isobutyric acid,valeric acid and isovaleric acid,the three BCAAs showed obvious combination effects (P<0.05).In conclusion,taking DMD as the index,when the CFR was 20:80,the best supplementation levels of valine,leucine and isoleucine were 0.67, 2.00 and 1.33 mmol/L,respectively, when the CFR was 40:60 or 60:40,it's not necessarily to add these BCAAs.